Mechanical weightlifting machine

ABSTRACT

A mechanical weightlifting machine in which the machine has a support structure with an elevated pivot having a pivot axis and an articulating mechanism engaging the pivot. The articulating mechanism having at least one articulating structure with a lever arm that has a depending link connected to the weight being used by the weightlifter. The articulating structure having an adjustment mechanism with a displaceable connection device connected to a counterweight. The adjustment mechanism having means for moving the displaceable connection device relative to the pivot axis and actuation means for actuating the means for moving, in order to vary the effective weight removed from or applied to the weight being used by the weightlifter.

RELATED APPLICATIONS

This patent application hereby incorporates by reference the followingU.S. patent applications and issued U.S. patents:

application Ser. No. 09/945,779;

application Ser. No. 09/277,806—now U.S. Pat. No. 6,283,898;

application Ser. No. 09/128,167; and

application Ser. No. 08/905,461—now U.S. Pat. No. 5,788,616,

FIELD OF THE INVENTION

This invention relates to a machine used in weightlifting exercises.

BACKGROUND OF THE INVENTION

A weightlifter can benefit from the active involvement of a secondperson, commonly known as a spotter, during a weightlifting routine.This spotter serves two basic functions. The first is to prevent injuryto the weightlifter. The second is to prolong the weightlifting exerciseby providing aid to the weightlifter during the weightliftingrepetitions. The second function allows the weightlifter to completeadditional repetitions after his or her muscles have begun to fatigue.Completing repetitions with slightly fatigued muscles can help theweightlifter improve muscle stamina and increase muscle mass.

Many weightlifters face the drawback of not having skilled spotters tohelp them on a consistent basis. As a result, these weightlifterssometimes do not achieve the results they seek and grow disheartenedwith the sport. In response, weightlifting facilities staff trainers towhom all weightlifters have equal access. Unfortunately, it isimpossible for only a few trainers to provide the services of a spotterto all these weightlifters at any one time.

In response to this drawback, inventors have designed user-controlledand microprocessor-controlled machines to serve both basic functions ofa spotter. Most of these machines rely either on an electric motor tolift the weight or on a pneumatic device to vary the assistance to theexerciser, both in response to some form of an input from the exerciser.

A shortcoming of these machines is that they usually use cables. Unlessthe cables are continuously taut throughout the exercise, they can movesuddenly, interfering with the exerciser's motion and causingdiscomfort.

Several of these machines also are not versatile enough to perform allthe functions of a spotter. In particular, a machine that uses a motorto pull up a weight can not perform several functions of a spotter. Aspotter can provide different amounts of assistance at different pointsin the exercise by applying different forces to the weight, while theexerciser applies the remainder of the force needed to counter gravity.Not until the very end of the exercise, if ever, does a spotter lift theweight out of the exerciser's hands. In theory, a motor can applydifferent forces as long as the voltage drop or the current across itcan be varied. But in application, activating a motor turns a rotor, inturn (possibly through a transmission) lifting the weight on its own.

Machines with pneumatic devices unfortunately may require severalseconds to vary the amount of assistance given to the exerciser, whereasa human spotter is able to provide the assistance immediately.

SUMMARY OF THE INVENTION

The object of the invention is to provide an apparatus that can performfunctions of a spotter with comfort, precision, and consistency.Therefore, a first objective is to be able to function without usingcables. A second objective is to be able to apply various differentforces to the exerciser's weight throughout a single routine, possiblyincluding a force great enough to raise the weight without assistancefrom the exerciser. A third objective is to be able to vary thisassistance quickly. A fourth objective is to be able to function withoutrestricting the exerciser's range of motion. A fifth objective is tofunction in a manner that safe and visible.

The mechanical weightlifting machine of the invention comprises asupport structure with an elevated pivot having a pivot axis. Anarticulating mechanism engaging the pivot has at least one articulatingstructure, and the articulating structure has at least one lever arm.Each lever arm has a distal end on one side of the pivot with aconnection device from which a depending link member is suspended. Thedepending link member has and end with means for engaging the bar of aweight. The articulating structure has an adjustment mechanism with adisplaceable connection device with a counterweight that has aneffective connection point locatable on the opposite side of the pivot.The adjustment mechanism has means for moving the displaceableconnection device and thus the effective connection point relative tothe axis of the pivot, wherein the leverage of the counterweightdirected to the lever arm is adjusted. Actuation means can actuate themeans for moving the displaceable connection device. A control deviceremote from the adjustment mechanism has control means for controllingthe actuation means.

BRIEF DESCRIPTION OF THE DRAWINGS

For a complete understanding of the above and other features of theinvention, reference is made to the following detailed description andthe accompanying drawings, wherein:

FIG. 1 is a perspective view of the weightlifting machine.

FIG. 2 is a side elevation view of the weightlifting machine of FIG. 1with one arm displaced from the other.

FIG. 3 is an enlarged cross sectional view taken on the line 3.3 in FIG.2.

FIG. 4 is an enlarged cross sectional view of a weight rest on theweightlifting machine of FIG. 1.

FIG. 5 is a top view of the weightlifting machine of FIG. 1.

FIG. 6 is a schematic view of an alternate displacement unit for theweightlifting machine of FIG. 1.

FIG. 7 is a bottom view of an alternate means for suspending a rod fromthe distal end of a lever arm of the weightlifting machine.

FIG. 8 is a perspective view of an apparatus that connects a weight tothe weightlifting machine of FIG. 1.

FIG. 9 is a side view of one half of the apparatus in FIG. 8, in an openposition.

FIG. 10 is a side view of one half of the apparatus in FIG. 8 in adifferently opened position, and with one side of its bracing angularlydisplaced from an in-line position.

FIG. 11 is a side view of a first embodiment of the adjustable rodsuspended from the distal end of a lever arm.

FIG. 12 is a side view of a second embodiment of the adjustable rodsuspended from the distal end of a lever arm.

FIG. 13 is a schematic view of a hand control device that can be used bysomeone other than the weightlifter.

FIG. 14 is an enlarged cross sectional view of an alternate design for aweight rest particularly suited for a dumbbell.

FIG. 15 is a perspective view of an alternate embodiment of theweightlifting machine of the present invention, wherein a singledisplacement unit may be used without restricting the range of motion ofeither a barbell or dumbbells for an exerciser.

FIG. 16 includes solid drawings of top, perspective, front, and sideviews of an alternate embodiment of the weightlifting machine verysimilar to that in FIG. 16.

FIG. 17 is an exploded view of the upper arm of the machine of FIG. 15.

FIG. 18 is a side view of an alternate embodiment of an adjustable frontlink in which the link is gimbaled to the bar of a barbell.

FIG. 19 is a side view of an alternate displacement unit comprising dual“square” rails.

FIG. 20 is a side view of an alternate displacement unit comprising asingle “square” rail.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

The mechanical weightlifting machine of this invention, designatedgenerally by the reference numeral 10, functions as a mechanicalspotter. The mechanical weightlifting machine 10, hereinafter thespotter, is used in many routines with a conventional bench 12 shown inphantom in FIG. 1. The. spotter can also accommodate inclining anddeclining benches, upright seats, and a standing exerciser without anybench. The spotter is used with weights in the form of conventionalplates or disks 16, two of which are shown in phantom in FIG. 1.

The spotter 10 is constructed with a support frame 18 having a base 20formed by interconnected box tube members 22 and wing-like stabilizermembers 24. The support frame 18 has a vertical support structure 25formed of substantially vertical box tube members 26 having a generallyrectangular or pyramidal structure with an apex cross beam 28. Box tubemembers 30 located approximately midway on the vertical support 24provide the necessary bracing to impart rigidity to the support framefor the range of uses and weights for which the apparatus wascontemplated. The box tube members are joined by welding or bolting andare customarily powder coated for appearance and protection.

The cross beam 28 supports a pivot shaft 30 to which an articulatingstructure 34 is attached for pivotal movement. The articulatingmechanism 32 preferably has two independently articulating structures 34to allow the mechanical spotter 10 to be used either with a barbell orwith dumbbells while only minimally restricting the exerciser's range ofmotion. Each articulating structure 34 has a projecting lever arm 36 aswell as an adjustment mechanism 46. Each articulating structure 34 canbe used alone without the operation of the other structure. Therefore, aspotter whose articulating mechanism 32 consists of a singlearticulating structure 34 may be suitable for a weightlifter whoexercises either with a barbell or with one dumbbell at a time. However,it is preferred that the articulating mechanism 32 have twoindependently articulating structures 34 for use either with a barbellor with two dumbbells simultaneously.

Each articulating structure 34 has a cantilever arm 36 with a distal end38. As shown in FIG. 1, each cantilever arm 36 has a right angle toprovide the appropriate spacing between the distal ends 38 of thearticulating structures 34. Alternately, each cantilever arm 36 may bestraight, and the cantilever arms 36 or the entire articulatingstructures 34 may be spaced apart from each other to provide theappropriate spacing at the distal ends 38. In addition, the straightcantilever arms could be positioned so they are slightly out of parallelwith each other when viewed from above, so that each arm articulatesabout a slightly different pivot axis.

From the distal ends 38 are suspended rods 40 with ends 42 that havemeans for engaging a bar (for example, a bar of a barbell or dumbbell).Each rod 40 is suspended from a distal end 38 by way of a connectiondevice, such as a universal joint. Each rod 40 may also be suspendedfrom a distal end 38 by way of the apparatus 151 shown in FIG. 7. InFIG. 7, the rod 40 is attached at the distal end 38 of the cantileverarm 36 by a carriage 152 that can both rotate about and slide along ashaft 150. If the rod 40 is fixed to the carriage 152, then the rod 40is always perpendicular to the shaft 150.

The means for engaging a bar at the rod ends 42 may comprise hooks,clasps, grooves, and/or collars. Preferably, the means for engaging donot restrict the natural range of motion of the weight as experienced bythe exerciser, or any restriction that results is only slight.Alternately, the means for engaging may include the more elaboratestructure shown in FIGS. 8, 9, and 10. As shown in FIG. 8, connected bypivoting joints 221 and 222 to each rod 40 is an apparatus 220 thatattaches to the bar (shown in phantom). This apparatus 220 is designednot to restrict any of the degrees of freedom or range of motion of theweight as experienced by the weightlifter. The weight is able to move,twist, turn, and rotate essentially as though it was not connected tothe spotter. The apparatus 220 is designed to adapt to all thickness andlengths of bars that a weightlifter might use. Also, the apparatus 220is designed not to interfere with the hands of the weightlifter.

The apparatus has at least one end 224, although the one shown in FIG. 8has two ends 224. Each end 224 has at least three wheels 226, while eachend shown in FIG. 8 has four wheels 226. The wheels 226 can have ribs togrip the bar more securely. The wheels 226 are positioned relative toone another to create a generally symmetric polygonal shape 228. Severalsides 230 of this shape 228 have adjustable lengths. To allowadjustment, the sides 228 incorporate the threaded rods 232.Alternately, the sides might incorporate springs (not shown) that causethe polygonal shape 228 to hug the bar.

Connected to a side 230 or a vertex of each of the preferably twopolygonal shapes 228 is an upside-down U-shaped member 234 designed toconnect the shapes 228 to each other while simultaneously notinterfering with a weightlifter's hands. This member 234 has two sides236 and a cross-support 238. The length of the cross-support 238 isadjustable, here by threaded rods 240, to provide a better fit for eachuser's hands. Each side 236 can incorporate a wheel 242 for rollingalong the inside of a dumbbell endplate in order to hold the dumbbellmore securely on the apparatus 220.

As shown in FIG. 9, each polygon 228 has a hinge 246 and a latch 248 foropening and shutting around the bar. The hinge 246 can be located ateither a vertex 250 or a side 230 of each polygon 228. The hinge 246 canalso have a torsional spring 252 to bias the polygon 228 in an open orshut position.

As shown in FIG. 10, the polygon 228 can alternately be built to openand shut by lengthening and shortening one of its sides 258. A latch 260would brace the polygon 228 in a shut position. Also, each side 236 ofthe upside-down U-shaped member 234 can have a pivoting joint 262 toallow it to be displaced angularly from a straight position to addcomfort to the weightlifter while performing certain exercises. Theupside-down U-shaped member 234, usually made either of a metal such asaluminum or of a hard plastic, can have a soft shell (such as a rubberone) for protection as well as for added comfort.

The rods 40 are adjustable in length to allow a weightlifter to use aflat bench, an inclining or declining bench, a seat, or to stand whileusing the spotter. If the lengths of the rods 40 are adjusted properly,the cantilever arms 36 should rise approximately 30° from the horizontaland lower approximately 30° from the horizontal during exerciserepetitions. This provides roughly a 30 inch displacement at the distalends 38 of the arms 36. Two possible embodiments of the adjustable rodsare shown in FIGS. 11 and 12.

In FIG. 11, the rod 40 has an inner section 160 that threadably engagesan outer section 162. Twisting the inner section 160 relative to theouter section 162 results in changing the overall length of the rod 40.The inner section 160 also engages a nut 168 that can be tightened upagainst the outer section 162 for the purpose of locking these twosections relative to each other. A universal joint 164 which connectsthe inner section 160 to a collar 166 allows this collar to move freelyabout the longitudinal axis of the inner section 160 as well as aboutany axis perpendicular to the longitudinal axis. This collar is onepossible means for engaging the bar of a barbell or dumbbell.

In FIG. 12, the rod 40 has a thicker section 170 and a narrower section174. The narrower section 174 is inserted into a hollow tube 172 forlinear movement therealong. The narrower section has apertures 176 thatcan align with other apertures 173 in the hollow tube 172. A pin 178that can selectively align these apertures together secures the hollowtube 172 in place along the rod 40. A screw 180 that threadably engagesa hole 181 in the hollow tube 172 presses against the narrower section174 to help in secure the hollow tube in place. A universal joint 182similar to the joint 164 connects the hollow tube 172 to a plate 184with a groove 185 into which the bar of a barbell or a dumbbell may beinserted. This groove can narrow at the end, as shown in phantom, inorder to accommodate bars with various diameters.

The arms 36 extend a short distance beyond the pivot shaft 30 and areconnected to counter weights 44. The size of each counter weight 44makes the user experience no additional force upon the exercise weightsaside from the force of the weights themselves, until the user sodesires.

The arms 36 of the articulating structures 34 are fixed to the shaft 30so that rotation of the shaft by the arms 36 also rotates a connectedadjustment mechanism 46 with a lever arm 48 having an adjustableeffective length. The spotter can be reset before a weightliftingroutine to make the effective length of this lever arm 48 equal to zero.Then, a rise in the effective length would create an upward force at therods 40, effectively varying the weight removed from the weight beingused by the exerciser.

Each lever arm 48 is connected by an elongated vertical link 50 toanother lever arm 52 with a distal end 54 equipped with a weight spindle56 for the optional addition of weight plates 16. The weight spindle 56provides for placement of one or more weights 16 to increase the rate ofweight adjustment as the effective length of the lever arm 48 changes,and to increase the maximum assistance provided when the effectivelength of the lever arm 48 is at its maximum. It is also possible toprovide an adjustment at the intersection of the vertical link 50 andthe lever arm 52 that allows this point of intersection to vary alongthe length of the lever arm 52. This adjustment would affect theleverage of the lever arm 52 and of any additional weight plates 16 uponthe vertical link 50, and in turn upon the lever arm 48.

A foot control 58 is electronically connected to a pair of drive motors60 either by a cord or by a cordless signal. The motors 60 have controlmeans that comprise an electronic controller circuitry associated withthe electric motors 60 for controlling the motors in response to controlsignals from the foot control 58. The control means have displacementmeans for displacing the motors by specified amounts in response tocontrol signals. Once the motors are displaced, the control means areable to prevent the motors from turning unless a control signal triggersanother displacement. For example, the controls means may includedevices such as a limit switch and an electronic brake; alternately, thedrive motors 60 may be servomotors. Activating the motors results inchanging the effective length of the lever arms 48 within the adjustmentmechanisms 46. It is possible to build the adjustment mechanism withoutmotors, so that the mechanical force from pressing on a pedal istranslated into a rotational force upon the ball screw. However, thespotter should be more user-friendly with electric control means thanotherwise with mechanical control means.

The foot control 58 has a toe strap 67 to permit bi-directional controlof the motor. For example, a lift action by the user's foot mightshorten the effective length of the lever arm 48 while a down pressuremight increase it. The foot control 58 might also come equipped with areset that returns the effective length of each lever arm 48 to zero.

The foot control 58 may be replaced by a head control (not shown) or bya hand control. The hand control may be designed for the weightlifter toactivate (not shown) or may be designed for use by a trainer or someoneelse overseeing the weightlifter's regimen. The latter is particularlysuited for a physical therapy facility where a trainer wishes to haveprecise control over the resistance of the weight. As shown in FIG. 13,the hand dial 210 has a digital display 212 and a numeric keypad 214 forentering the amount of weight placed onto the spotter. Buttons labeled“H” and “L” increase and decrease the amount of assistance,respectively. A rotary dial 216 allows for a fine adjustment of theamount of assistance. A reset button 218 resets the adjustmentmechanisms to their original positions.

As shown in FIGS. 2 and 3, the elongated links 50 have a point ofeffective connection to the carriage 195 where screws 196 fasten thelinks 50 to the carriage 195 through bearings 197. The adjustmentmechanism 46 when activated displaces this effective connection pointfrom a position proximate the axis of the pivot shaft 30 to a positiondisplaced from the shaft 30 with the effect of changing the effectivelength of the lever arm 48. For example, in FIG. 2, the effectiveconnection point within each adjustment mechanism 46 is moved toward thedistal end of the shroud 66. FIG. 3 shows one embodiment of thedisplaceable connection device 199. In FIG. 3, the adjustment mechanism46 includes an outer shroud 66 that forms a housing for two shafts 191that guide the displaceable connection device 199 by way of linearbearings 190. The carriage portion 195 of the displaceable connectiondevice 199 is displaced by means for moving it, here for examplecomprising a ball screw 192 that engages a nut 194 fastened to thecarriage 195, where the screw 192 is actuated by a drive motor 60. Analternate embodiment of the links 50 is shown in phantom in FIG. 3,where the two links join to form a single link. When the links 50 aredisplaced from a position proximate the axis of the pivot shaft 30, theeffect is to translate the generally downward force, including the forcefrom the counterweight of the displaceable connection device 199 as wellas from the separate counterweights 16, into a generally upward force atthe rods 40.

The spotter can also effectively add weight to the weight being used bythe exerciser. If the adjustment mechanism 46 is extended past the pivotshaft 30 in the direction of the distal end 38 of the cantilever arm 36,then positioning the effective connection point on this side of thepivot shaft 30 has the effect of translating the generally downwardforce from the weights 16 into a generally downward force at the rods40.

To limit the downward swing of the arms 36, the support frame 18 isequipped with stops 72 that can prevent a downward angle exceeding, forexample, 45°. Similarly, other stops (not shown) can be fastened to theapex cross beam 28 to limit the upward travel of the arms 36.

The support frame 18 includes a pair of weight rests 74 mounted to thevertical members 26 on the side of the support structure from which thearms 36 extend. The rests 74 are shown in greater detail in the enlargedview of FIG. 4. The rests 74 have a collar 76 that encircles thevertical members 26 and a retractable pin 78 that engages one of aseries of holes 80, allowing vertical adjustment of the rest 74. Aweight support 82 is connected to the collar 76 and projects from thecollar 76 to provide a flat seat 84 for the bar 86 of a barbell ordumbbell, shown in phantom. An end stop 88 prevents the bar from rollingoff the seat 84 and additionally provides a blunt end for inadvertentcontact. The pin 78 is retracted against a compression spring 90 by atrigger 92 connected to the pin 78 and protected by a guard 94.

To provide additional safety for barbell users, the weight supports 82of the weight rests 74 might be designed to extend even farther out awayfrom the vertical members 26 of the frame 18. For example, the supports82 might extend all the way out to the exerciser's shoulders. Thisdesign would permit an exerciser to place the barbell onto the weightrests 74 more easily in the event that this exerciser could not lift theweight, even with the full assistance from the spotter.

An alternate design of a weight rest suited specifically for dumbbellsis shown in FIG. 14. This weight rest 200 attaches to the support frame18 similarly to the weight rest 74 shown in FIG. 4. The weight rest 200has seats 202 suited for resting a dumbbell thereon. A space between theseats 202 makes it easy for the exerciser to use the weight rest 200reaching in from beneath it. Walls 204 prevent the dumbbell from fallingout of the rest 200.

The arrangement of the adjustment mechanism 46 to the cantilever arm 36in each articulating structure 34 is shown in the top view of thespotter in FIG. 5.

Alternately, the cantilever arm 36 and the adjustment mechanism 46 canbe combined into a single articulating unit as shown in the alternateembodiment of FIG. 6.

An alternate embodiment of the articulating unit 100 is shownschematically in FIG. 6. With the exception of the combined cantileverarm and remainder adjustment mechanism, forming the integratedarticulating unit 100, the remainder of the apparatus is the same asthat of the previously described embodiment. The cantilever arm 102 is ahollow box 104 that provides a housing for the adjustment mechanism 106.The cantilever arms 102 are spaced to allow connection of the elongatedvertical links 50 to the adjustment mechanism 106. An extension 108 ofthe cantilever arms 102 on the opposite side of the pivot shaft 30 formsa housing for the movable internal carriage. The carriage 110 isthreadably connected to a ball screw 112 in a manner similar to thatshown in FIG. 3. A drive motor 114 is housed within the arm 102 and isconnected to the adjustment screw 112 for displacement of the carriage110 on activation of the motor in a forward or reverse direction. Thearticulating unit 100 is designed along with the rods 40, the ends 42,and their engaging means, to make the user experience no additionalforce upon the exercise weights aside from the force of weightsthemselves, until the user so desires, while the carriage 110 has itseffective pivotal connection in a position proximate the axis of thepivot shaft 30.

Although only foot, hand, and head controls have been mentioned foractivating the adjustment mechanisms, it is possible to use other meansinstead. One possibility is to make the adjustment mechanisms displacethe effective pivotal connections after the weightlifter has completed apreprogrammed number of repetitions by incorporating switches into thecantilever arms for counting the number of repetitions. Anotherpossibility is to make the adjustment mechanisms displace the effectivepivotal connections once the user has been stationary for a presetlength of time, since this is most likely when the user needsassistance.

For safety, the spotter can have an alarm that sounds when the effectivepivotal connection is at the distal end of the adjustment mechanism andthe maximum assistance is being provided. This noise would alert theweightlifter not to initiate any additional repetitions but instead toplace the weight back onto its rests.

Because the spotter is designed to connect to a bar of weight, it issuited for use with traditional free weights, including primarilybarbells and dumbbells. However, the spotter is also suited for use withother weightlifting machines that use similar bars, such as the “Smith”machines on which a bar is connected to vertical tracks.

While, in the foregoing, specific embodiments of the present inventionhave been set forth in considerable detail for the purpose of making acomplete disclosure. of the invention, it may be apparent to thoseskilled in the art that numerous changes can be made in such detailwithout departing from the spirit and principles of the invention.

Changes may similarly be made to the following embodiments withoutdeparting from the spirit and scope of the present invention.

As shown in FIG. 15, the frame 501 of the weightlifting machinepreferably includes a base section 502 and three approximately centrallylocated upright tubular sections 504. The three upright sections 504 areattached to each other and to two additional upright tubular sections506 of a front rack 508 by two s-shaped braces 512, which bracespreferably comprise circular tubes. The s-shaped braces 512 areconfigured to leave an open user region 514 for a user to standproximate the rack 508 and are configured to permit easy entry to theuser region 514 from the side of the machine, e.g., when the barbell 516is racked or even as the machine is in use if someone else wishes tointerfere with the exercise set. In a manner similar to that in theforegoing embodiments, a bench, seat, or the like may be convenientlypositioned for the user in the region 514 proximate the rack in order toincrease the variety of weight training exercises available. Thes-shaped braces 512 advantageously increase the stability of the overallframe 50). The braces are preferably flange-mounted to the rear of eachof the two upright members 506 of the rack in order to preventinterference with the hands of a user. The rack sections 506 either maybe positioned vertically or may be positioned to lean back slightly,e.g., by anywhere between approximately two and seven degrees, as isknown in the art in order to provide additional comfort to the user upon“breaking” the barbell.

In contrast with the earlier embodiments of the invention, the upper armstructure includes a C-shaped front section 530 pivotally connected tothe adjustment mechanism 532 in a manner shown by the arrow 500. Thispivotal connection advantageously permits the barbell 516 (or dumbbells)to have a full and unfettered range of motion, in a manner similar tothat of the earlier embodiments. Specifically, the C-shaped section 530may turn with respect to the adjustment mechanism 532 about thelongitudinal axis of the adjustment mechanism. In addition, only asingle rear elongated link 50 and single lower lever arm 534 aretherefore required. The lower lever arm preferably includes weightspindles 536 extending in both directions to carry additional weightplates, or alternately a single circular bar extending symmetricallythrough the lower lever arm. The lower lever arm is preferably pivotallyconnected to the front of the three central uprights 504, e.g., by meansof housed bearing, flanged bearings, journal bearings, or the like. Inthe preferred embodiment, the effective point of the pivotal connection500, the pivot shaft 30, the effective connection point between thecarriage and the rear elongated link 540, and the effective connectionpoints between the front links 541 and the C-shaped section 530 are allcoplanar.

The pivot shaft preferably comprises two separate shafts mounted tohoused ball bearing units 552 attached to each respective side of theadjustment mechanism. A gap 556 between the adjustment mechanism andeither supporting upright section, provided by the s-shaped braces 512,provides sufficient spacing for the housed ball bearing units.

The frame and the C-shaped section are each preferably modular and maybe bolted together for increased strength and convenience of assembly,disassembly, shipping, and manufacture. While the effective length ofthe cantilever arm, i.e. the effective distance between the pivot shaft30 and the connection points between the front links 541 and theC-shaped section 530 is preferably approximately 42 inches, thisdistance may range substantially (e.g., between 20 inches and 70 inchesor even between lower, lower limits and higher, higher limits). Theupper arm structure preferably remains in the angular range between 30degrees below the horizontal and 30 degrees above the horizontal duringuse. The displaceable carriage 558 of the actuator preferably, althoughnot necessarily, is capable of being displaced by approximately 20inches rearward from the pivot shaft. Front hooks 560 are preferablydesigned to prevent the barbell from falling of the rack when a forwardforce is applied to the barbell, without the simultaneous application ofa net upward force to the barbell. For example, the hooks may turnupwardly in front of the barbell to prevent the barbell from falling.Electronic equipment such as the drive, controller, power supply, etc.may be safely and conveniently positioned in the space provided at thebase 502 of the machine within the three central upright members 504.Any of a variety of footswitches, such as the 2-way switch 570 shown,may be easily connected to the controller, and the wire 572 from thefootswitch may be safely positioned inside the tubular sections.Similarly, the leads (ground, hot, etc.) from the controller to themotor may be positioned inside the upright tubular sections.

FIG. 16 shows solid drawings of top, perspective, front, and side viewsof an alternate embodiment of the weightlifting machine very similar tothat in FIG. 16, the main exception being the configuration of theS-shaped braces.

FIG. 17 shows an exploded view of the upper arm of the machine of FIG.15. The C-shaped 530 section preferably comprises three tubular sections580 bolted together with flanges 582. The adjustment mechanism 532houses the actuator 590 as well as an internal rod structure 610. Therod structure 610 comprises a solid rod 612, preferably having anapproximately one inch diameter at threaded at one end, welded within ahollow rectangular box. The box is inserted into and bolted within theactuator housing 620. The motor 630 (stepper motor, servomotor, DCmotor, ac motor, etc.) is preferably positioned at the end of thehousing 620 opposite the rod structure 610. In the preferred embodiment,attached to the central tube of the C-shaped section are two housed ballbearing units 640 as well as two journal bearings 645. Upon assembly,the rod is inserted into an aperture of the central tube proximate thehoused bearings 640, and a nut 650 threadably engages the rod, resultingin a strong, easily manufactured, and easily assembled pivotalconnection. Housed bearing units 552 are also provided on either side ofthe housing 620 for easy assembly. A channel in the bottom wall of theactuator housing 620, as shown in FIG. 15, is provided for the rearelongated link 50 to enter the housing and attach to the carriage of theactuator.

FIG. 18 is a side view of an alternate embodiment of an adjustable frontlink 541 in which the link 541 is gimbaled to the bar of the barbell516. Specifically, the barbell is inserted into three collars 700. Theouter two are fastened to the barbell, e.g., with a set screw, and thecentral collar is allowed to pivot about the barbell. The central collaris also pivotally connected to a yoke assembly attached to the frontlink, e.g., with shoulder bolts 702 and flanged ball bearings 704, as isknown in the art. A universal joint such as a ball-type joint 706 ispositioned at the top end of the link. Two pins 708 may be removed topermit adjustment of the length of the link. The pins are preferablythreadably attached to removable clasps 710, whereby the clasps and thepins may be tightened together in order to squeeze the inner and outersections of the adjustable links, in turn preventing any slop or play inthe links which might otherwise exist.

FIG. 19 shows a side view of an alternate displacement unit comprisingdual “square” rails 800. A ball screw 810 is pivotally mounted to endblocks 812 by ball bearings, as is well known in the art. A ball nut 814(hidden) is inserted into the carriage 816. The carriage is attached,e.g., bolted, to two linear bearings 818. The linear bearings are inturn fastened to linear rails, such as square rails 820, as is wellknown in the art. The square rails are preferably bolted to the baseplate 822 of the actuator. Upon assembly, the actuator would be turned“upside down,” whereby the base plate is bolted to the upper wall (i.e.the ceiling) of the actuator housing and within the housing. A motor 824is attached to an end of the ball screw with a coupling 826 or the like.Shoulder bolts 828 may be used to attach the yoke assembly to thecarriage, with ball bearings, journal bearings, etc., resulting in thepoint of effective connection 195 proximate the ball screw.

An alternate embodiment of the linear slide is shown in FIG. 20, inwhich the displacement unit includes only a single “square” rail. Thesingle linear rail (e.g., square rail) in FIG. 20 is preferably largerand stronger than the dual rails in FIG. 19, for it typically must carrytwice the load of each of the dual rails. In addition, it iscontemplated that any other number of rails may be used. It is alsocontemplated that the rails may have any of a variety of configurations,including not only square but circular, hybrid, etc. It is alsocontemplated that the linear rails, as well as the bearing blocks forthe ball screw, may be mounted directly to the interior of theadjustment mechanism housing, effectively eliminating the need for theactuator base plate as long as the housing has sufficient strength andwall thickness.

All tubular sections of the upper arm structure are preferably aluminumin order to reduce the swing weight (inertia) if the structure in use.However, it is contemplated that the actuator housing may be composedinstead of stainless steel or carbon steel in order to provideadditional strength as well as weight in order to balance the upper armstructure when the machine is in its neutral position (effectivelyeliminating the need for counterweights 44 in FIG. 1). The physicalprinciples of the machine, including the point of zero assistance,remain very similar with the single upper structure as they were withthe dual upper arms.

Additional advantages resulting from the single upper arm structureinclude:

No longer a risk that both motors are not perfectly synchronous, thatone will malfunction, or that one will wear faster and thus run moreslowly than the other. Instead, both sides of the barbell will alwaysfeel the same amount of assistance. In addition, there is no longer arisk that the mechanical components of one stage will wear 2Z fasterthan those of the other. Fewer parts to replace.

The central upright members may be provided with integral weight treesfor convenience, where the spindles are pointed outwardly. The uprighttubes of the rack may also be provided with weight trees with thespindles pointed out.

If weight plates are removed from one side of the barbell at a time,there is a lower likelihood that the entire barbell will fly up from therack if the machine is not in its neutral position.

If a user inadvertently places more counterweight on one side of themachine than on the other, there is no resulting asymmetry inassistance.

Provides a visual indication to the exerciser if the barbell is tiltedduring an exercise set.

1. A mechanical weightlifting machine, comprising: (i) a supportstructure having an elevated pivot with a pivot axis; (ii) anarticulating mechanism engaging the pivot, the articulating mechanismhaving at least one articulating structure, the articulating structurehaving an upper arm structure having front and rear ends, wherein theupper arm structure includes a front section rotatable about thelongitudinal axis of the upper arm structure, the front section havingfirst and second distal ends on the front side of said pivot axis fromwhich first and second depending link members are suspended, eachdepending link member having an end with means for engaging a bar, thearticulating structure having an adjustment mechanism with adisplaceable connection device with an effective connection pointlocatable on the opposite side of the pivot, the displaceable connectiondevice having a counterweight; (iii) means for moving the displaceableconnection device relative to the axis of the pivot wherein the leverageof said counterweight directed to said upper arm structure is adjusted;(iv) actuation means for actuating said means for moving; and (v) acontrol device remote from the adjustment mechanism with control meansfor controlling said actuation means.